How much distance should a labrador run everyday?

I am trying to figure this one out! I have two dogs - a female chocolate lab and a golden retriever - both are 2.5 years old.

We have built them up running since they were young - starting out with short distance. Now in the morning I run them 7km - about 50mins and then at night my partner runs up to 10km with them - so we are talking at least 15km most days - if not more.

My partner has had them up to 17km in one run.

They are tired when they get home and tend to sleep but when they are out there is no stopping them! They chase each other like mad things - they get off the lead most of the way and get to swim too so it is a busy run for them.

Anyway - they seem to love this amount of outdoor activity :)